Element concentrations of aluminosilicate components from ODP sites in the Pacific Ocean

We measured major and trace element concentrations in the operationally defined, chemically extracted, residual aluminosilicate component of sediment from Ocean Drilling Program Sites 1215 and 1256 in the central and eastern equatorial Pacific Ocean and found that this residual component contains volcanogenic and authigenic aluminosilicates in addition to inferred eolian material. While the residual component younger than 20 Ma from the central Pacific (ODP Site 1215) is similar compositionally to upper continental crust and suggests an increase in the delivery of Asian dust material since 20 Ma, the residual in sediment older than 20 Ma indicates significant amounts of volcanogenic and authigenic materials. Volcanogenic debris comprises as much as ~ 40% of the residual between 23-40 Ma, which coincides with the mid-Tertiary "ignimbrite flare-up" that occurred in much of western North America. The residual component extracted from the 50 Ma biogenic sediment reflects authigenic signatures (seawater-like negative cerium anomalies and elevated Fe/Si ratios). The previously interpreted increase in an andesitic detrital source in North Pacific locations may instead be authigenic material, presenting significant challenges for many paleoclimate proxies. Additionally, in the eastern Pacific (ODP Site 1256), the residual component contains ~70% of volcanogenic material, most likely originating from Central America, and also includes refractory barite. The ability to separately identify eolian, volcanogenic, and authigenic materials in the aluminosilicate component of pelagic sediment allows resolution, respectively, of the climatic, geologic, and chemical processes contributing to the paleoceanographic archive in this critical oceanic region.

Organic carbon and amino acid concentration of Karelian shungite rocks from the lake Onego area, Russia

The study of amino acids in the Precambrian shungite rocks of Karelia showed that their contents vary within 25-89 µg/g depending on proportions between shungite and mineral components. It was established that the amino acids exhibit an excess of L-enantiomers. In the shungite rocks, they form organomineral complexes with silica and aluminosilicates, being built in the globular structure of shungite matter. There are several sources of amino acids in shungites: secondary synthesis, microbial pollution, and original amino acids of organic matter in shungite rocks.

Mineral and chemical compositions of a ferromanganese nodule from Station DM41-3911-76

Processes of authigenic manganese ore formation in sediments of the North Equatorial Pacific are considered on the basis of a study of the surface layer (<2 mm) of a ferromanganese nodule and four micronodule size fractions from associated surface sediment (0-7 cm). Inhomogeneity of nodule composition is shown. Mn/Fe ratio is maximal in samples from lateral sectors of the nodule at the water-sediment interface. Compositional differences of nodules are related to preferential accumulation of trace elements in iron oxyhydroxides (P, Sr, Pb, U, Bi, Th, Y, and REE), manganese hydroxides (Co, Ni, Cu, Zn, Cd, Mo, Tl, W), and lithogenic component trapped during nodule growth (Ga, Rb, Ba, and Cs). Ce accumulation in the REE composition is maximal in the upper and lower parts of the nodule characterized by minimal Mn/Fe values. A compositional comparison of manganese micronodules and surface layers of the nodule demonstrates that micronodule material was subjected to more intense reworking during diagenesis of sediments. The micronodules are characterized by higher Mn/Fe and P/Fe, but lower Ni/Cu and Co/Ni ratios. The micronodules and nodules do not differ in terms of contents of Ce and Th that are the least mobile elements during diagenesis. Differences in chemical composition of the micronodules and nodules are related not only to additional input of Mn in the process of diagenesis, but also to transformation of iron oxyhydroxides after removal of Mn from the close association with Fe formed in suspended matter during sedimentation.